Rabbit haemorrhagic disease virus (RHDV) was illegally released in New Zealand in August 1997. The initial release and spread of the virus was conducted by landholders in an effort to reduce costs associated with more conventional control methods (poisoning and shooting). Serum was collected from wild rabbits throughout the Otago region prior to the release and from 13 sites in the months following the first epizootic.
Following the occurrence of the first RHDV epizootic on 13 pastoral farming properties a range of survival rates was found. The major factor influencing the survival rate was found to be the method of release, with widespread use of carrot or oat baits containing RHDV resulting in poor kills.
Widespread use of baits also resulted in higher levels of antibody in surviving adult rabbits with a higher proportion of adult females surviving the epizootic, compared with properties where the disease was allowed to spread naturally. A correlation was found between survival rate and the percentage of surviving adults with high levels of antibody.
These results suggest that poor
kill rates are not due to poor spread of the virus, that the
large-scale use of baits resulted in protective immunisation and that
rabbit control should in the future be achieved through establishing
naturally spreading epidemics rather than widespread use of baits.
More New Zealand Research showing RCD baits immunise rabbits
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